Lamotrigine

Introduction

Gabapentin is an anticonvulsant medication used to treat epilepsy and to delay or prevent the recurrence of depressive episodes in bipolar disorder. Lamotrigine is FDA-approved therapy for the form of epilepsy known as Lennox-Gastaut syndrome. It reduces the frequency of seizures.

Pronunciation

Lamotrigine 50mg

Generic Name 藥名	HA Code 藥物代碼	Classification藥物分類
Lamotrigine Tablet 50mg	LAMO01	P1S1S3

Mechanism of Action

Anticonvulsant medication. It inhibits the sodium channels leading to stabilization of neuronal membrane

Dosage

Epilepsy

By mouth as monotherapy: the initial oral dose for use as monotherapy is 25 mg once daily for 2 weeks followed by 50 mg once daily for 2 weeks; thereafter the dose is increased by a maximum of 50 to 100 mg every 1 to 2 weeks to usual maintenance doses of 100 to 200 mg daily in 1-2 divided doses.

As adjunct to therapy but not taking valproate, the dosage regime is as for monotherapy.

In those taking valproate, the initial oral dose of lamotrigine is 25 mg every other day for 2 weeks followed by 25 mg once daily for 2 weeks; thereafter the dose is increased by a maximum of 25 to 50 mg every 1 to 2 weeks to usual maintenance doses of 100 to 200 mg daily in 1-2 divided doses.

Bipolar disorder

Monotherapy without valprate:	initially 25 mg once daily for 14 days, then
	50 mg daily in 1-2 divided doses for further 14 days, then
	100 mg daily in 1-2 divided doses for further 7 days.
	Usual maintenance 200 mg daily in 1-2 divided doses
	Max. 400 mg daily
Adjunctive therapy with valproate:	initially 25 mg on alternate days for 14 days, then
	25 mg once daily for further 14 days, then
	50 mg daily in 1-2 divided doses for further 7 days;
	Usual maintenance 100 mg daily in 1-2 divided doses;
	Max. 200 mg daily

Administration in children

*2-12 years:	initially 300 micrograms/kg daily in 1-2 divided doses for 14 days, then
	600 micrograms/kg daily in 1-2 divided doses for further 14 days, thereafter
	Increased by max. 600 micrograms/kg every 1-2 weeks.
	Usual maintenance 1-10 mg/kg daily in 1-2 divided doses.
	Max. 200 mg daily.

The use and doses of lamotrigine in children over 12 years of age is as for adults.

Side Effects

Adverse drug reactions associated with the use of pregabalin include:

Very common (>10% of people with lamotrigine)	Dizziness, drowsiness
Common (1-10% of people with lamotrigine)	Blurred vision, diplopia, Ataxia Aggression Agitation Back pain Tremor Nausea and vomiting
Rare (<0.1% of people with lamotrigine)	Blood disorders, anaemia, leucopenia Exacerbation of Parkinson’s disease Hallucination Hepatic failure Hypersensitivity syndrome Lupus erythematosus-like reactions

Lamotrigine binds to the eye and melanin-containing tissues which can accumulate over time and may cause toxicity. Prescribers should be aware of the possibility of long-term ophthalmologic effects and base treatment on clinical response.

Serious skin reactions including Stevens-Johnson syndrome and toxic epidermal necrolysis have developed; most rashes occur in the first 8 weeks of start of therapy.